Downhole vibration apparatus and methods

ABSTRACT

A method of extending an earthen bore comprises the steps of rotating a drill bit at the end of a tubular while vibrating the tubular. The method results in reduced friction to tubular advance through the bore and results in stabilized drill bit loading and longer usable drill bit life. A method of conditioning a cement slurry in an annulus between a casing and a bore to improve a resulting cement liner comprises the steps of coupling a vibration generator to the casing, running the casing into the bore, displacing the cement slurry into the annulus and using the vibration generator to vibrate the casing. A vibration generator may comprise a mass, having a mass center, coupled to a frame, a motor and a power source to spin the mass about an axis offset from the mass center.

STATEMENT OF RELATED APPLICATIONS

This application depends from and claims the benefit of U.S. ProvisionalPatent Application No. 61/155,601 filed on Feb. 26, 2009.

FIELD OF THE INVENTION

This application relates to the drilling of an earthen bore, cementingof a casing in an earthen bore, improving drill bit service life andimproving bonding between a cement liner installed around a casing in anearthen bore.

BACKGROUND

It is conventional practice to couple a drill bit to a tubular, forexample, a drill string, and to rotate the drill bit against an end ofan earthen bore to extend the bore into the earth's crust. A drillstring may comprise slick (i.e., constant diameter) drill collars orenlarged (relative to the mid-section of the joints) drill collars. Incasing while drilling applications, the drill bit is coupled to acasing. Drill cuttings are removed from the bore by circulating drillingfluid through a fluid passage in the drill string (which, in drillingapplications, may be a drill string or a casing) to the drill bit, andback to the surface through an annulus between the drill string and theearthen bore. As the drill bit penetrates the earth's crust, the drillstring advances through the bore at a rate of penetration of the drillbit. In conventional drilling operations, the drill string may rotatealong with the drill bit. In some drilling operations, such as casingwhile drilling, the drill bit may rotate independently of the drillstring using a bottom hole assembly (BHA) that includes a mud motorpowered by pressurized drilling fluid to rotate the drill bit. Theweight or load imparted to the drill bit by the drill string is a factorthat determines the rate of penetration.

In drilling operations, it is advantageous to stabilize the rate ofadvance of the drill string through the borehole to prevent unwantedspikes in the load imparted to the drill bit. Intermittent or sporadicadvances of the drill string within the bore may cause drill bit damagedue to excessive loading. This problem may be greater in bores having ahighly deviated section due to substantially greater frictionalresistance between the bore and the drill string. In highly deviatedsections of a bore, the weight of the drill string (and contents) bearon the floor, or downwardly disposed side, of the bore to causesubstantially greater frictional resistance to advance of the drillstring through the bore. The result may be intermittent and erraticadvances of the drill string and related peak loads imparted to thedrill bit.

An attempt to stabilize the rate of advance of a drill string through abore having a highly deviated section uses an oscillating valve disposedwithin a BHA coupled to the drill string. Pressurized drilling fluid maybe pumped through the fluid passage in the drill string to drive theoscillating valve to vibrate the BHA and reduce frictional resistance toadvance of the drill string through the bore.

An oscillating valve powered by pressurized drilling fluid may consume asubstantial portion of the mechanical energy provided to the BHA,leaving less mechanical energy to drive the mud motor and/or tocirculate and remove drill cuttings.

After an earthen bore is drilled to a targeted depth, it is conventionalpractice to cement a casing in the bore to prevent collapse andstabilize the bore. A float device, such as a float shoe or a floatcollar, may be coupled to the casing, and the casing may be run into thebore and positioned within a targeted interval. The casing may also beradially positioned (or “centered”) within the bore using casingcentralizers, such as bow spring centralizers, coupled at intervalsalong the casing to provide an annulus between the casing and the bore.Cement slurry is pumped through the casing with cementing plugs tofacilitate displacement of the slurry through the float device and intothe annulus. The cement slurry solidifies to provide a protective cementliner around the casing. Alternately, an inner cementing string may berun through the casing and stung into a mandrel, for example, a mandrelin a float device, and cement slurry may be delivered through the innercementing string and the float device to the annulus.

The quality of the cement liner may be improved by conditioning thecement slurry within the annulus while and/or or after the cement slurryis displaced into the annulus. The cement slurry may be conditioned byagitation to induce turbulent fluid flow, disrupt fluid channeling andpromote bonding of the cement liner to the bore.

Reciprocation and/or rotation of the casing using the drilling rig areconventional methods of agitating a cement slurry. In substantiallyvertical bores, where casing hangs primarily in tension, casing is moreeasily reciprocated and/or rotated within the bore. In bores havinghighly deviated sections, reciprocating or rotating the casing may bedifficult because the weight of the casing (and contents) bears heavilyon the floor, or downwardly disposed side, of the bore. As a result,casing rotation and/or reciprocation within a highly deviated section ofa bore causes unwanted wear and stress on the casing, on the casingcentralizers and on rig equipment used to move the casing within thebore.

What is needed is a method to stabilize the advance of a tubular, suchas a drill string, through an earthen bore to prevent excessive drillbit loading. What is needed is a method to condition a cement slurrydisplaced into an annulus between a tubular, such as a casing, and abore. What is needed is a method to condition an annular flow or volumeof cement slurry around a casing without imparting unwanted stress andwear on the casing, casing centralizers and rig equipment.

SUMMARY

One embodiment of the invention is a method of stabilizing drill bitloading to extend the usable life of a drill bit comprising the steps ofcoupling a drill bit to a drill string (which may be a casing used in acasing while drilling application), coupling a vibration generator tothe drill string, coupling a power source, such as a battery, to thevibration generator, running the drill string into a bore to engage thedrill bit with an end of the bore, rotating the drill bit to extend thebore, and activating the vibration generator to vibrate a portion of thedrill string within a highly deviated section of the bore to reducefrictional resistance to advance of the drill string and therebystabilize drill bit loading.

Another embodiment of the invention is a method of reducing frictionalresistance to advance of a tubular through a highly deviated section ofa drilled earthen bore comprising the steps of coupling a vibrationgenerator to the tubular, e.g., a casing, coupling a power source, suchas a battery, to the vibration generator, running the tubular into abore, and activating the vibration generator to vibrate a portion of thetubular within a highly deviated section of the bore to reducefrictional resistance to advance of the casing and thereby stabilizeadvance of the casing through the bore towards the targeted interval.

Another embodiment of the invention is a method of conditioning a cementslurry to promote improved bonding between a cement liner and a borecomprises the steps of coupling a float device (such as a float shoe ora float collar) to a casing, coupling a vibration generator to thecasing, coupling a power source (such as a battery) to the vibrationgenerator, running the casing into a bore, displacing a volume of cementslurry through the casing and the float device and into an annulusbetween the casing and the bore, and activating the vibration generatorto vibrate a portion of the casing to condition a portion of the volumeof cement slurry adjacent the vibration generator.

In the methods described above, the vibration generator may beactivatable using a pressure sensor disposed in communication with thepower source to detect an activating condition. For example, in oneembodiment, a pressure sensor may be disposed to detect the pressure ina fluid passage in the drill string, the casing, in a sub or in thefloat device. The pressure sensor may be coupled to a microprocessorprogrammed to monitor readings of the pressure sensor and to recognizean activating condition or sequence. For example, but not in the way oflimitation, the pressure sensor may detect a first predeterminedpressure threshold, followed by a pressure trough lasting for apredetermined interval of time, followed by a second predeterminedpressure threshold, altogether comprising a sequence of eventsrecognizable by the microprocessor. In response, the microprocessor mayclose an electrical circuit to provide current from the a power sourceto a motor to activate the vibration generator. A subsequentpredetermined event or sequence may be used to deactivate the vibrationgenerator.

One embodiment of the method of conditioning a cement slurry maycomprise coupling the vibration generator to a float device, such as afloat shoe or float collar. Another embodiment of the method ofconditioning a cement slurry may comprise coupling the vibrationgenerator to one or more drillable components, such as a float device,so that the vibration generator and the float device may be drilled ordestroyed to provide an unrestricted passage through the casing tofacilitate further extension of the bore after the cementing step.

An embodiment of an apparatus that may be used to implement a methoddescribed above comprises a mass rotatably coupled within a frame andhaving a mass center, a motor coupled to the mass, and a power sourcecoupled to the motor to provide energy for spinning the mass on an axisoffset from the mass center to produce reactive vibrations in the frame.

A power source for providing energy to a motor may, in one embodiment,comprise a battery having a high power-density including, but notlimited to, a nickel-cadmium battery, a nickel-metal-hydride battery ora lithium-ion battery. While high power-density batteries may providefor optimal performance of the vibration generator, a conventional leadacid battery may also be used.

A mass to be spun to produce vibrations may, in one embodiment, comprisean elongate member of a high density material, such as lead, or it maycomprise a substrate to which weighted attachments are secured toprovide a mass center offset from an axis about which the mass is spun.It will be understood that factors affecting the frequency and magnitudeof vibrations includes the weight of the mass, the offset between theaxis of rotation and the mass center, the angular velocity of spinningof the mass and the relative size of the sub, float device or otherframe to which the mass is secured.

The foregoing, as well as other, objects, features, and advantages ofthe invention will be more fully appreciated and understood by referenceto the drawings, described below, and to the claims appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a drilling rig on the earth's surface and adrill string extending from the rig into an earthen bore.

FIG. 1A is a section view taken at position 1A-1A along the drill stringof FIG. 1.

FIG. 2 is a section view of one embodiment of a vibrating sub having avibration generator and coupled within a drill string adjacent a drillbit.

FIG. 3 is an illustration of a drilling rig on the earth's surface and acasing being installed in a targeted interval in a highly deviatedsection of the bore.

FIG. 3A is a section view taken at position 3A-3A along the casing ofFIG. 3.

FIG. 4 is a section view of an alternate embodiment of a drill subhaving a vibration generator.

FIG. 5 is a section view of an embodiment of a float device having avibration generator.

DETAILED DESCRIPTION

FIG. 1 is an illustration of a drilling rig 1 on the earth's surface 5and a tubular 8 extending from the rig 1 into an earthen bore 2 drilledinto the earth's crust 3. A drill bit 50 and a vibration generator 10are coupled to the tubular 8. The vibration generator 10 is illustratedin FIG. 1 as being disposed within a highly deviated section 7 of thebore 2. A highly deviated section 7 is a section of the bore 2 disposedat a substantial angle from vertical. The highly deviated section may behorizontal. The tubular 8 in FIG. 1 may comprise a drill string or acasing, the latter being likely in casing while drilling applications.

FIG. 1A is a section view taken at position 1A-1A on FIG. 1. FIG. 1Aillustrates the nature of the frictional resistance to advance of thetubular 8 and a bore 2 in a highly deviated section (see referencenumber 7 of FIG. 1A) of the bore 2. FIG. 1A illustrates how the weightof the tubular 8 (and contents) bears downwardly on the supportingfloor, or downwardly disposed side, of the bore 2. The large reactionforce applied by the bore 2 to support the tubular 8 substantiallyincreases frictional resistance to advance of the tubular 8 through thebore 2.

FIG. 2 is an enlarged section view of the embodiment of the vibrationgenerator 10 of FIG. 1 comprising a sub 12 having a first threadedconnection 12A, a second threaded connection 12B, and a fluid passage 22therebetween. The fluid passage 22 illustrated in FIG. 2 deviates froman axis 88 of the tubular 8. The first threaded connection 12A of thesub 12 is coupled to a mating connection 8A of an adjacent tubularsegment 8B of the tubular 8, and the second threaded connection 12B ofthe sub 12 is coupled to a mating connection 50A of the drill bit 50(not shown in section) disposed against the end 2A of the bore 2. Thevibration generator 10 of FIG. 2 comprises a mass 14 rotatably coupledto the sub 12, a motor 18 coupled to the mass 14 and a power source 20coupled to the motor 18 through electrical conduit 29. Activation of themotor 18 using the power source 20 spins the mass 14 on an axisincluding the axle first portion 14A and axle second portion 14B, butoffset from a mass center 14C.

FIG. 3 is an illustration of a drilling rig 1 on the earth's surface 5and a casing 30 disposed in a targeted interval in a highly deviatedsection 7 of the bore 2. A plurality of centralizers 52 are received onthe casing 30 at intervals along the casing 30 to provide an annulus 28between the casing 30 and the bore 2. A float device 60 is coupled tothe casing 30 to facilitate displacement of cement slurry from a fluidpassage (not shown) within the casing 30 and into the annulus 28.

FIG. 3A is a section view taken at position 3A-3A along the casing ofFIG. 3 and illustrates the stand-off between the casing 30 and the bore2 provided by the bow springs 52 a of the centralizer 52. The resultingannulus 28 receives a cement slurry 69 therein to form a cement linerupon curing of the cement slurry. As can be seen in FIG. 3A, vibrationof the casing 30, especially vibration having a radial displacement aswill be generated by the apparatus illustrated in FIGS. 3, 4 and 5, willcondition the cement slurry 69 within the annulus 28 and promoteimproved cement liner bonding to the bore 2.

FIG. 4 is a section view of an alternate embodiment of a vibrationgenerator 30 comprising a sub 32 having a first connection 30A withthreads 31A, a second connection 30B with threads 31B, a fluid passage42 therebetween, and a vibration generator 30 comprising a mass 34, amotor 38 coupled to the mass 34, and a power source 40 coupled to themotor 38 through an electrical conduit 49. Activation of the motor 38using the power source 40 spins the mass 34 on an axis including axlefirst portion 34A and axle second portion 34B but offset from a masscenter 34C to vibrate the sub 32 and a tubular (not shown in FIG. 4—seeFIG. 3).

FIG. 5 is an enlarged section view of the float device 62 of FIG. 3. Thefloat device 62 comprises a threaded connection 60A at which it may becoupled to a casing (see FIG. 3—float device is illustrated in FIG. 5decoupled from the casing). The float device 62 further comprises avibration generator comprising a mass 66 rotatably coupled to the floatdevice 62, a motor 68 coupled to the mass 66, and a power source 64coupled to the motor 68. Activation of the motor 68 using the powersource 64 spins the mass 66 about an axis including axle first portion66A and axle second portion 66B but offset from a mass center 66C. Thefloat device 62 of FIG. 5 further comprises a module 67 comprising apressure sensor and a microprocessor. The module 67 is in fluidcommunication with a fluid passage inlet 61 within the threadedconnection 60A through a channel 67A in the float device 62. The fluidpassage inlet 61 is separated from a fluid passage outlet 63 by a checkvalve comprising a ball 57 movably captured between a restriction 59 anda spring 58. It will be understood that the ball 57 is disposed by thespring 58 against the restriction 59 to prevent flow through therestriction 59 until the pressure in the fluid passage inlet 61 exceedsthe pressure in the fluid passage outlet 63 by a differential that issufficient to overcome the force of the spring 58 against the ball 57,at which time fluid (not shown) will flow from the fluid passage inlet61, past the ball 57, through the fluid passage outlet 63 and throughthe exit port 74. Operating in this manner, the float device 62 preventsfluid within the bore 2 (see FIG. 3) from flowing into the fluid passageinlet 61 and entering the casing 30 (see FIG. 3).

The terms “comprising,” “including,” and “having,” as used in the claimsand specification herein, shall be considered as indicating an opengroup that may include other elements not specified. The terms “a,”“an,” and the singular forms of words shall be taken to include theplural form of the same words, such that the terms mean that one or moreof something is provided. The term “one” or “single” may be used toindicate that one and only one of something is intended. Similarly,other specific integer values, such as “two,” may be used when aspecific number of things is intended. The terms “preferably,”“preferred,” “prefer,” “optionally,” “may,” and similar terms are usedto indicate that an item, condition or step being referred to is anoptional (not required) feature of the invention.

From the foregoing detailed description of specific embodiments of theinvention, it should be apparent that an apparatus and a method forstabilizing the advance of a tubular through a bore that is novel hasbeen disclosed, and that an apparatus and a method for conditioning acement slurry in an annulus has been disclosed. Although specificembodiments of the apparatuses and methods are disclosed herein, this isdone solely for the purpose of describing various features and aspectsof the invention, and is not intended to be limiting with respect to thescope of the invention. It is contemplated that various substitutions,alterations, and/or modifications, including but not limited to thoseimplementation variations which may have been suggested herein, may bemade to the disclosed embodiments without departing from the spirit andscope of the invention as defined by the appended claims which follow.

While embodiments of the invention have been described herein, variousmodifications of the apparatus and method of the invention may be madewithout departing from the spirit and scope of the invention, which ismore fully defined in the following claims.

1. A method of advancing a tubular through a highly deviated portion ofan earthen bore comprising the steps of: coupling a vibration generatorto a tubular; running the tubular into the bore to dispose the vibrationgenerator within the highly deviated section; and activating thevibration generator to vibrate a portion of the tubular within thehighly deviated section of the bore.
 2. The method of claim 1 furthercomprising the steps of: coupling a drill bit to the tubular; androtating the drill bit against an end of the bore.
 3. The method ofclaim 2 wherein the tubular is a drill string.
 4. The method of claim 2wherein the step of rotating the drill bit against the end of the borecomprises the steps of: coupling a mud motor to the drill bit; andproviding a flow of pressurized fluid to the mud motor to rotate thedrill bit.
 5. The method of claim 1 wherein the step of coupling avibration generator to a tubular comprises the steps of: coupling a masshaving a mass center to the tubular; coupling a motor to the mass;coupling a power source to the motor; and activating the motor to spinthe mass on an axis offset from the mass center.
 6. The method of claim1 further comprising the steps of: coupling a float device to thetubular; displacing a volume of cement slurry through the tubular andthe float device and into an annulus between the tubular and the bore;and conditioning a portion of the volume of cement slurry within thehighly deviated section.
 7. The method of claim 1 further comprising thesteps of: coupling a second vibration generator to the tubular;disposing the second vibration generator within the highly deviatedsection; and activating the second vibration generator to vibrate asecond portion of the tubular within the highly deviated section of thebore.
 8. The method of advancing a tubular through a highly deviatedsection of an earthen bore comprising the steps of: coupling a masshaving a mass center to a tubular; coupling a motor to the mass;coupling a power source to the motor; running the tubular into theearthen bore to position the mass within the highly deviated section ofthe bore; and spinning the mass on an axis offset from the mass centerto vibrate a portion of the tubular adjacent the mass.
 9. The method ofclaim 8 wherein the power source is a battery and the motor is anelectrically-driven motor.
 10. A method of extending an earthen borecomprising the steps of: coupling a drill bit and a vibration generatorto a tubular; running the tubular into the bore; rotating the drill bitagainst an end of the bore; and vibrating the tubular using thevibration generator.
 11. The method of claim 10 further wherein the stepof vibrating the tubular using the vibration generator comprising thesteps of: coupling a mass having a mass center to a tubular sub;coupling a motor to the mass; coupling a power source to the motor; andactivating the motor to spin the mass about an axis offset from the masscenter.
 12. The method of claim 10 wherein the step of rotating thedrill bit against the end of the bore comprises the step of: fluidicallydriving a mud motor to rotate the drill bit relative to the tubular. 13.The method of claim 10 further comprising the step of: coupling a secondvibration tool to the tubular; and vibrating the tubular using thesecond vibration tool.
 14. A method of conditioning a volume of cementslurry disposed within an annulus between a tubular and an earthen boreinto which the tubular is run, comprising the steps of: coupling avibration generator to the tubular; displacing the volume of cementslurry through the bore of the tubular and into the annulus; andactivating the vibration generator to vibrate the volume of cementslurry.
 15. The method of claim 14 wherein the step of coupling avibration generator to the tubular comprises the steps of: rotatablycoupling a mass having a mass center to the tubular; and coupling amotor to the mass; coupling a power source to the motor; and activatingthe motor to spin the mass on an axis offset from the mass center. 16.The method of claim 15 further comprising the step of coupling a floatdevice to the tubular.
 17. The method of claim 16 wherein the floatdevice is at least one of a float collar and a float shoe.
 18. Themethod of claim 17 wherein the float device comprises a check valve. 19.The method of claim 14 wherein the step of coupling a vibrationgenerator to the tubular comprises the steps of: providing a sub havinga first threaded connection at a first end coupled to the tubular, asecond threaded connection at a second end, and a fluid passagetherebetween in fluid communication with the bore of the tubular. 20.The vibration tool of claim 14 wherein the sub further comprises asecond threaded connection at a second end of the fluid passage.
 21. Thevibration tool of claim 14 wherein the sub further comprises a floatshoe having a valve.